Metallic frame and method of making the same

ABSTRACT

An exemplary metallic frame ( 60 ) is formed by forging and precise machining of a workpiece. The forging process is performed before the precise machining process, a hardness of the frame is larger than that of the workpiece and a surface roughness Ra of the frame reaches about 6.4 microns. The present invention further provides a method of making the frame. The method includes as follows: feeding workpiece process ( 12 ) for providing a workpiece ( 20 ); forging process ( 14 ), the workpiece be forged to form a preform ( 40 ); and precise machining process ( 18 ), the preform be precisely machined to form a frame.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a metallic frame and a method of makingthe same.

2. Discussion of the Related Art

Nowadays, various electronic devices such as mobile phones, personaldigital assistants, and laptop computers are popular and used in avariety of situations. The electronic devices are not only desired withmultifunctionality, but also desired being robustness and foraesthetics. Therefore, metal is widely used in frames of the electronicdevices.

One typical method of making metallic frame (herein typical framemanufacturing process) includes coarse milling of a workpiece and thenprecise milling of the workpiece. The frame made from the typical framemanufacturing process has a high precision in size and shape and a lowsurface roughness. However, a machining period is very long using thetypical frame manufacturing process because the milling process is timeconsuming. As an example, the machining period of the typical framemanufacturing process requires more than ten hours when producing aframe of an ordinary mobile phone. Thus, a production efficiency of themethod is low. In addition, a cost of milling is high, adding to ahigher production cost of the frame. Furthermore, during coarse millingand precise milling, a significant amount of material is removed fromthe workpiece and wasted. This also adds to the higher production costof the frame. Referring to FIGS. 7-9, a frame made of grade SUS304Istainless steel (SUS304I is a Japanese grade of this type of stainlesssteel, and a corresponding Chinese grade is OCr19Ni11) using the abovemethod shows a metallographic photograph of the frame took under 23±5degrees Celsius (° C.) and 40-80% relative humidity (RH) conditions. Theinternal structure of the frame is magnified by 50×, 100×, and 200× inFIGS. 7-9 respectively. The metallographic structure of the frameincludes austenite and delta ferrite. A Vickers hardness of the frameunder 23±5° C., 40-80% RH and 0.5 kilogram (kg) is 169. Therefore, ahardness of the frame is unduly low.

Therefore, a metallic frame which has high hardness and low productioncost and method of making the metallic frame are desired.

SUMMARY

An exemplary metallic frame is formed by forging and precise machiningof a workpiece. The forging process is performed before the precisemachining process, a hardness of the frame is larger than that of theworkpiece and a surface roughness Ra of the frame reaches about 6.4microns.

An exemplary method of making the frame is provided. The methodincludes: feeding workpiece process for providing a workpiece; forgingprocess, the workpiece being forged to form a preform; and precisemachining process, the preform being precisely machined to form a frame.

Other advantages and novel features will become more apparent from thefollowing detailed description when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the drawings are not necessarily drawn to scale, theemphasis instead being placed upon clearly illustrating the principlesof the present metallic frame and method of making the same. Moreover,in the drawings, like reference numerals designate corresponding partsthroughout the several views, and all the views are schematic.

FIG. 1 is a flow chart of a method of making a metallic frame of thepresent invention.

FIG. 2 is a workpiece formed in a process of the method of FIG. 1.

FIG. 3 is a preform formed after a forging process of the method of FIG.1.

FIG. 4 is a preform formed after a hole defining process of the methodof FIG. 1.

FIG. 5 is a frame formed after a milling process of the method of FIG.1.

FIG. 6 is a metallographic photograph of the frame of FIG. 5.

FIG. 7 is a metallographic photograph of a traditional frame magnifiedby in 50×.

FIG. 8 is a metallographic photograph of a traditional frame magnifiedby 100×.

FIG. 9 is a metallographic photograph of a traditional frame magnifiedby 200×.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention provides a metallic frame and a method of makingthe same. The metallic frame usually employed in electronic devices suchas mobile phones, personal digital assistants, and laptop computers.

Referring to FIG. 1, the method of making the metallic frame includesthe following:

-   (1) Feeding workpiece process 12: Referring to FIG. 2, a workpiece    20 is provided by cutting a steel sheet. A size of the workpiece 20    is determined according to a size and a shape of the frame design.    In the embodiment, the workpiece 20 is made of SUS304I stainless    steel;-   (2) Forging process 14: Referring to FIG. 3, the workpiece 20 is    forged several times by a forging equipment (not shown) with a    forging mold (not shown), thereby yielding a preform 40. In the    forging process 14, the workpiece 20 is managed without being heated    by external heat. After the forging process 14, the preform 40 has a    size and a shape similar to but a little different from the frame    design. For example, the preform 40 is slightly larger and does not    have holes compared with the frame design. The preform 40 includes a    main portion 402 and a flange 404 extending along an edge of the    main portion 402. In the embodiment, the main portion 402 has a    shape formed by a rectangle and two semi-circulars with a linear    edge adjoining to two opposite edges of the rectangle.    Alternatively, the preform 40 may also not include the flange 404,    and the main portion 402 may also be of any shapes. The size and the    shape of the preform 40 are determined according to a size and a    shape of the frame design;-   (3) Hole defining process 16: Referring to FIG. 4, a hole 406 is    defined in the preform 40. Also, two or more holes can be defined in    the preform 40; and-   (4) Milling process 18: Referring to FIG. 5, the preform 40    undergoes precise milling. A surface of the preform 40 is milled    yielding a frame 60 according to the frame design. The precise    milling process 18 is shorter than the milling process in the    typical metallic frame making method because the size and the shape    of preform 40 closely matches the frame design. Furthermore, the    frame 60 has a high precision in size, shape, and surface roughness.    A surface roughness of the frame 60 is in a range from 2.5 microns    (μm) to 0.6 μm after precise milling process 18.

During the forging process 14, the stainless steel material is extruded,squeezed, and forged such that the internal metallographic structure ischanged and refined. Thereby, mechanical properties, hardness, and wearresistance of the frame 60 are improved.

Referring to FIG. 6, a metallographic photograph got under 23±5 degreesCelsius (° C.) and 40-80% relative humidity (RH) is shown. In FIG. 6,the metallographic structure is magnified by 200×. The metallographicstructure of the frame 60 includes austenite. Comparing FIG. 6 with FIG.7, it can be seen that a metallographic structure is changed. The changeof the metallographic structure results in the improvement of themechanical properties, the hardness and the wear resistance of the frame60. Furthermore, in this embodiment, a Vickers hardness of the frame 60under 23±5° C., 40-80% RH and 0.5 kilogram (kg) is 348 (in thespecification, all values of hardness are average values of a pluralityof tests) which is much larger than the frame made by milling only.Generally, the Vickers hardness can reach 300.

During the forging process 14, no material is removed from the workpiece20. During the milling process 18, little material is removed from theworkpiece 20 because the size and the shape of the preform 40 are quiteclose to the frame 60. Therefore, little material is wasted and aproduction cost of the frame 60 is low. Furthermore, an efficiency ofthe forging process 14 is much higher than the milling process of thetypical frame manufacturing process, and a cost of the forging process14 is also much lower than milling. Therefore, a production efficiencyof the present method for making the frame 60 is high, and a productioncost of the frame 60 is low.

Alternatively, other machining processes such as edge-cutting andpolishing can be added to make a frame with needed size, shape, andsurface properties etc. If a needed frame design does not have a hole,the hole defining process 16 is omitted. The milling process 18 may alsobe replaced by other precise machining process such as turning processand planing process. After the precise machining process, a surfaceroughness can reach 6.4 μm. The surface roughness can even reach 3.2 μm.

It is believed that the present embodiments and their advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made thereto without departing from the spiritand scope of the invention or sacrificing all of its materialadvantages, the examples hereinbefore described merely being preferredor exemplary embodiments of the invention.

1. A metallic frame is characterized that the frame is formed by forgingand precise machining a workpiece, and the forging process is performedbefore precise machining, a hardness of the frame is larger than that ofthe workpiece and a surface roughness Ra of the frame reaches about 6.4microns.
 2. The frame as claimed in claim 1, wherein the frame is madeof stainless steel.
 3. The frame as claimed in claim 2, wherein theframe is made of SUS304I.
 4. The frame as claimed in claim 3, wherein anaverage Vickers hardness of the frame reaches about
 300. 5. A method ofmaking a metallic frame, a hardness of the frame is larger than that ofthe workpiece and a surface roughness Ra of the frame reaches about 6.4microns, the method comprising: feeding workpiece process for providinga workpiece; forging process, the workpiece is forged to form a preform;and precise machining process, the preform be precisely machined to forma frame.
 6. The method as claimed in claim 5, wherein in the precisemachining process, the preform is machined by milling process.
 7. Themethod as claimed in claim 5, wherein the workpiece is provided bycutting a steel sheet, and a size of the workpiece is determinedaccording to a size and a shape of a frame design.
 8. The method asclaimed in claim 5, wherein the preform has a size and a shape accordingto the frame design.
 9. The method as claimed in claim 5, furthercomprising at least one of processes of edge-cutting, hole defining, andpolishing.
 10. The method as claimed in claim 5, wherein in the forgingprocess, a metallographic structure is changed, and the change of themetallographic structure results in the improvement of the mechanicalproperties, the hardness and the wear resistance of the frame.
 11. Themethod as claimed in claim 5, wherein the frame is made of SUS304I. 12.The frame as claimed in claim 11, wherein an average Vickers hardness ofthe frame reaches about 300.